Circuit arrangement for operating electrostatic loud speakers



Sept. 26, 1933. RE sz 1,928,503

CIRCUIT ARRANGEMENT FOR OPERATING ELECTROSTATIC LOUD SPEAKERS Filed Dec. 19, 1928' INVE/V 70 Eugen, Rezsz AT ORNFYJ Patented Sept. 26, 1933 CIRCUIT ARRANGEMENT FOR OPERATING ELECTROSTATIC LOUD SPEAKERS Eugen Reisz, Berlin-Dahlem, Germany Application December 19, 1928, Serial No. 326,996, and in Germany November 10, 1927 2 Claims.

This invention relates to improved circuit arrangements for electrostatic loud speakers. As is well known such loud speakers have hitherto requireda comparatively high operating voltage and it is an object of the present invention to enable an electrostatic loud speaker to be operated with a direct current voltage supply of from comparatively low potential (110 to 220 volts).

According to this invention the acoustic fre quency alternating current energy which the loud speaker is to convert into sound, is utilized to raise the working potential of the said loud speaker to a the necessary high value, whereby greater modulation is obtained.

The invention is illustrated in the accompanying diagrammatic drawing.

Referring to the drawing, alternating currents of acoustic frequency and derived from a receiver or from a microphone or other source are applied through an input transformer 1 to the grids g and 1 of amplifier valves 2) and v1, arranged in pushpull connection. The filaments of valves 12, v1, and also that of a rectifier valve (to be referred to later) are heated from a common source j which also provides anode potential to the valves v, 111.

Amplified currents from the valves 11 and v1 flow through the primary winding a of a step-up transformer 2, and produce in the secondary winding 19 of the said transformer, alternating potentials which are applied through the rectifier c and serve to charge a condenser (11, so that the point 3 becomes negative and the point 4 positive. The point 3 is connected through a resistance 10 of high ohmic value to one of the conductive plates or coatings of an electrostatic loud speaker e, while the point 4 is connected to the negative terminal of the source 1 of direct current. The loud speaker e thus obtains a positive charge from the positive terminal of the source I through one portion of the winding a, the potential difi'erence across the said loudspeaker being equal to the sum of the potential differences across the said source 1 and across the condenserdl.

Alternating potentials are applied to the loud speaker from the points or terminals 5 and 6 0f the primarywinding a of thetransformer 2, the latter pointer terminal being connected through a blocking condenser d. It will be seen that with this arrangement the amplifier valves 12, 121 can in series in the heating circuit for the filaments of the valves 01, v and 0.

Thus, the low frequency alternating current received by the loud speaker is used in part for acoustical sensitizing and in part-by means of rectificationfor producing the field of static electricity.

It will be appreciated that owing to the fairly high insulating resistance of the loud speaker e, the charge in the condenser d1 substantially does not leak away, so that the said condenser assumes a substantially constant charge corresponding to the maximum amplitude of the alternating currents.

I claim: i

1. A circuit arrangement for operating an electrostatic loud speaker, comprising a source of acoustic frequency alternating current which the loud speaker is to convert into sound, a source of direct current, a condenser in series with the direct current source to the potential of which its potential is added, means for converting the direct current into acoustic frequency alternating current to be added to the first named alternating current, means for amplifying the combined alternating currents, a transformer for stepping-up the said amplified alternating currents, a second condenser, and means for rectifying a portion of the said alternating currents to raise the'working potential of the loud speaker to the requisite high value, the secondary of the transformer being arranged to charge the second condenser through the rectifying means.

2. A circuit arrangement for operating an electrostatic loud speaker, comprising a source of acoustic frequency alternating current which the loud speaker is to convert into sound, a source of direct current, means for converting the direct current into acoustic frequency alternating current to be added to the first named alternating current, means for amplifying the combined alternating currents, a step-up transformer having its primary winding connected to the said amplifying means and to the terminals of the loud speaker, a rectifier valve connected to the secondary winding of said transformer and through it to the negative side of the direct current source, a blocking condenser connected in circuit with and between the said transformer secondary winding and the direct current source, and a connection, including a resistance, leading from a point between said condenser and the adjacent terminal of the said transformer secondary winding and connecting one side of the loud speaker.

EUGEN REISZ. 

